This application is based upon and claims benefit of priority of Japanese Patent Applications No. Hei-11-46884 filed on Feb. 24, 1999 and No. Hei-12-6180 filed on Jan. 11, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a matrix-type display panel such as a liquid crystal display panel and to a display device that includes a display panel and apparatus to drive the panel.
2. Description of Related Art
A display panel having pixels arranged in a matrix and scanning electrode stripes and data electrode stripes which run perpendicularly to the scanning electrode stripes is generally known. Scanning voltages are usually given to the scanning electrodes sequentially, for example, from the top of the panel toward the bottom.
It is also known to perform interlaced scanning by jumping a certain number of scanning electrodes to reduce flicker on the displayed image. In the sequential scanning, a scanning interval between one electrode and an electrode next scanned is Tv/n, where Tv is a time required to scan all the scanning electrodes and n is the number of scanning electrodes. In the interlaced scanning performed by jumping p electrodes, the scanning interval is Tv/(p+1). This means that the scanning moves quicker from the top to the bottom, and a viewer of the display feels as if the scanning frequency increased by (p+1) times. In this manner, flicker on the displayed image can be decreased to a certain level. However, if a space in which the (p+1) electrodes are included is large enough to be seen by a viewer, and if the scanning frequency is not sufficiently high, a phenomenon called a line scroll appears on the display. The line scroll which is detrimental to display quality is such a phenomenon that horizontal stripes move upward or downward on the display.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved matrix-display panel and its driving device in which the flicker and the line-scroll are suppressed and made invisible.
The matrix-display panel is composed of row electrodes Yj, column electrodes Xi running perpendicularly to the row electrodes, and an electro-optical material such as antiferroelectric liquid crystal interposed between both electrodes. Pixels G(i,j) arranged in a matrix are formed at each intersection of both electrodes Yj an d Xi. One display line is constituted by the pixels G(i,j) aligned in line along a row electrode Yj. Scanning voltages are supplied to the row electrodes from a scanning electrode driving circuit, while image data signal voltages are supplied to the column electrodes from a data electrode driving circuit in synchronism with the scanning voltages. The scanning voltages are combined with the data signal voltages, and the combined voltages are imposed on the pixels.
The pixels G(i,j) aligned in line along a row electrode Yj are connected alternatively to Yj and the next row electrode Y(j+1) in a zigzag manner. The row electrodes are scanned in an interlaced manner by jumping one electrode, i.e., in the order of Y1, Y3, Y5 . . . Yn. In this manner, a flicker frequency becomes two times of the driving frequency, or a frame frequency. For example, when the panel is driven by 30 Hz, the flicker frequency becomes 60 Hz which is invisible. The line-scroll is also made invisible at the same time.
Alternatively, the pixels G(i,j) aligned in line along the row electrode Yj are connected to three row electrodes Yj, Y(j+1) and Y(j+2), i.e., connecting a pixel G(i,j) to Yj, a pixel G(i+1,j) to Y(j+1), and a pixel G(i+2,j) to Y(j+2). The following pixels are connected to the same three row electrodes in a reversed order, making a zigzag connection as a whole. In this case, the interlaced scanning is performed by jumping two row electrodes every time. In this manner, the flicker frequency becomes three times of the frame frequency, e.g., when the frame frequency is 20 Hz, the flicker frequency becomes 60 Hz which is invisible to a viewer. At the same time, the line-scroll becomes invisible.
The pixels G(i,j) may be replaced with pixels that are switched by a transistor connected to each pixel. In this case, gate electrodes of transistors connected to the pixels aligned in line along the row electrode Yj are alternately connected to neighboring two electrodes Yj and Y(j+1), and the interlaced scanning is performed by jumping one row electrode. Alternatively, the pixels aligned in line along the row electrode Yj are connected to three neighboring electrodes Yj, Y(j+1) and Y(j+2) in a zigzag manner, and the interlaced scanning is performed by jumping two row electrodes every time. The flicker frequency becomes two times or three times of the frame frequency according to the respective arrangements.
Each pixel may be divided into two sub pixels or three pixels each corresponding to respective colors red, green and blue, and neighboring pixels may be driven by alternating polarities, thereby further reducing the flicker on the displayed images.